The relationship between the radius of the nucleus $(R)$ and the mass number $(A)$ is given by .......

Among the following,the correct statement about the cathode ray discharge tube is:

Fill in the blanks:
$(i)$ For the discovery of neutrons,$\alpha$-particles were bombarded on a thin sheet of ......... .
$(ii)$ For the $\alpha$-particle scattering experiment,Rutherford used a gold foil of thickness ......... .
$(iii)$ The radius of an atom is approximately ......... and the radius of the nucleus is ......... .
$(iv)$ The entire positive charge of an atom is concentrated in a very small region,which is called ......... .

An atom is defined as :

The nature of anode rays depends upon:

When beryllium is bombarded with $\alpha$-particles,extremely penetrating radiations which cannot be deflected by electrical or magnetic field are given out. These are